Hypo + Hypernatraemia Flashcards
What is hypernatremia?
High plasma Na+ conc
>146mmol/L
Causes of hypernatremia
- osmotic diuresis e.g. uncontrolled diabetes
- fluid loss without replacement e.g. sweating, burns, vomiting
- diabetes insipidus
- incorrect IV fluid replacement
- primary aldosteronism
Symptoms of hypernatraemia
- thirst
- apathy
- irritability
- weakness
- confusion
- reduced consciousness
- seizures
- hyperreflexia + spasticity
- coma
What is apathy?
a lack of motivation or lack of interest in things around you
Different types of hypernatremia + their causes
Hypovolaemic hypernatraemia
- osmotic diuresis
- loop diuretics
- intrinsic renal disease
- excessive sweating
- burns
- diarrhoea
.
- Euvolaemic hypernatraemia:
- diabetes insipidus
- hypodipsia
.
Hypervolaemic hypernatraemia:
- primary hyperaldosteronism
- Cushing’s syndrome
- hypertonic dialysis
- sodium chloride tablets
Treatment of hypernatraemia
- identify underlying cause + reverse if possible
- increase water intake
- IV fluids dextrose in water - no sodium
- monitor sodium levels
Symptoms of hyponatraemia
- headache
- N+V
- malaise
- confusion
- agitation
- drowsiness
- gait imbalance
Investigations of hyponatraemia
- plasma osmolality
- urine osmolality
- urine Na+
- TFTs
- cortisol levels
- CT head if suspected SIADH
- drug history
- hydration status
Diagnostic pathway of hyponatarmia
- exclude non-hypo-osmolar hyponatraemia (e.g. hyperglycaemia)
- then check urine osmolality
- urine osmolality <100mosmol/kg - primary polydipsia or inappropriate IV fluids
- urine osmolality >100mosol/kg - check urine Na
- urine Na >30mmol/L - GI loss, CCF, nephrotic syndrome, cirrhosis
- urine Na <30mmol/L - SIADH, vomiting, primary salt wasting, Addison’s disease
What does a urine sodium of >30mmol/l suggest?
Low effective arterial volume
due to true dehydration *e.g. GI salt loss
Or CCF, cirrhosis or nephrotic syndrome
What does urine sodium >30mmol/L suggest?
if euvolaemic - SIADH
if dehydrated - Addison’s disease, renal + cerebral salt wasting + history of vomiting
What causes hypovolaemic hyponatremia?
Renal losses:
- thiazide diuretics
- osmotic diuresis
- Addison’s disease
.
Non- renal losses:
- diarrhoea
- vomiting
- seating
- burns
- pancreatitis
Why does vomiting cause hyponatramia?
causes loss of H+ > metabolic alkalosis
corrected by renal excretion of sodium bicarbonate
What drugs can cause hyponatremia?
- thiazides
- SSRIs
- PPIs
- ACEi
- loop diuretics
Treatment of hypovolaemic hyponatraemia
- give IV fluids: 0.9% saline at 1-3ml/kg/hour
- give K+ if needed
